diff options
Diffstat (limited to 'docs/manual/mod/mod_file_cache.html.en')
| -rw-r--r-- | docs/manual/mod/mod_file_cache.html.en | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/docs/manual/mod/mod_file_cache.html.en b/docs/manual/mod/mod_file_cache.html.en new file mode 100644 index 0000000..8f0bd52 --- /dev/null +++ b/docs/manual/mod/mod_file_cache.html.en @@ -0,0 +1,238 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head> +<meta content="text/html; charset=UTF-8" http-equiv="Content-Type" /> +<!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>mod_file_cache - Apache HTTP Server Version 2.4</title> +<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> +<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> +<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" /> +<script src="../style/scripts/prettify.min.js" type="text/javascript"> +</script> + +<link href="../images/favicon.ico" rel="shortcut icon" /></head> +<body> +<div id="page-header"> +<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p> +<p class="apache">Apache HTTP Server Version 2.4</p> +<img alt="" src="../images/feather.png" /></div> +<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div> +<div id="path"> +<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.4</a> > <a href="./">Modules</a></div> +<div id="page-content"> +<div id="preamble"><h1>Apache Module mod_file_cache</h1> +<div class="toplang"> +<p><span>Available Languages: </span><a href="../en/mod/mod_file_cache.html" title="English"> en </a> | +<a href="../fr/mod/mod_file_cache.html" hreflang="fr" rel="alternate" title="Français"> fr </a> | +<a href="../ko/mod/mod_file_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p> +</div> +<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Caches a static list of files in memory</td></tr> +<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Experimental</td></tr> +<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>file_cache_module</td></tr> +<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_file_cache.c</td></tr></table> +<h3>Summary</h3> + + + <div class="warning"> + This module should be used with care. You can easily create a broken + site using <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code>, so read this document + carefully. + </div> + + <p><em>Caching</em> frequently requested files that change very + infrequently is a technique for reducing server load. + <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> provides two techniques for caching + frequently requested <em>static</em> files. Through configuration + directives, you can direct <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> to either + open then <code>mmap()</code> a file, or to pre-open a file and save + the file's open <em>file handle</em>. Both techniques reduce server + load when processing requests for these files by doing part of the work + (specifically, the file I/O) for serving the file when the + server is started rather than during each request.</p> + + <p>Notice: You cannot use this for speeding up CGI programs or + other files which are served by special content handlers. It + can only be used for regular files which are usually served by + the Apache core content handler.</p> + + <p>This module is an extension of and borrows heavily from the + <code>mod_mmap_static</code> module in Apache 1.3.</p> +</div> +<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><h3>Topics</h3> +<ul id="topics"> +<li><img alt="" src="../images/down.gif" /> <a href="#using">Using mod_file_cache</a></li> +</ul><h3 class="directives">Directives</h3> +<ul id="toc"> +<li><img alt="" src="../images/down.gif" /> <a href="#cachefile">CacheFile</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#mmapfile">MMapFile</a></li> +</ul> +<h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mod_file_cache">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mod_file_cache">Report a bug</a></li></ul><h3>See also</h3> +<ul class="seealso"> +<li><a href="#comments_section">Comments</a></li></ul></div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="using" id="using">Using mod_file_cache</a></h2> + + <p><code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> caches a list of statically + configured files via <code class="directive"><a href="#mmapfile">MMapFile</a></code> or <code class="directive"><a href="#cachefile">CacheFile</a></code> directives in the main server configuration.</p> + + <p>Not all platforms support both directives. You will receive an error + message in the server error log if you attempt to use an + unsupported directive. If given an unsupported directive, the + server will start but the file will not be cached. On platforms + that support both directives, you should experiment with both to + see which works best for you.</p> + + <h3>MMapFile Directive</h3> + + <p>The <code class="directive"><a href="#mmapfile">MMapFile</a></code> + directive of <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> maps a list of + statically configured files into memory through the system call + <code>mmap()</code>. This system call is available on most modern + Unix derivatives, but not on all. There are sometimes system-specific + limits on the size and number of files that can be + <code>mmap()</code>ed, experimentation is probably the easiest way + to find out.</p> + + <p>This <code>mmap()</code>ing is done once at server start or + restart, only. So whenever one of the mapped files changes on the + filesystem you <em>have</em> to restart the server (see the <a href="../stopping.html">Stopping and Restarting</a> documentation). + To reiterate that point: if the files are modified <em>in place</em> + without restarting the server you may end up serving requests that + are completely bogus. You should update files by unlinking the old + copy and putting a new copy in place. Most tools such as + <code>rdist</code> and <code>mv</code> do this. The reason why this + modules doesn't take care of changes to the files is that this check + would need an extra <code>stat()</code> every time which is a waste + and against the intent of I/O reduction.</p> + + + <h3>CacheFile Directive</h3> + + <p>The <code class="directive"><a href="#cachefile">CacheFile</a></code> + directive of <code class="module"><a href="../mod/mod_file_cache.html">mod_file_cache</a></code> opens an active + <em>handle</em> or <em>file descriptor</em> to the file (or files) + listed in the configuration directive and places these open file + handles in the cache. When the file is requested, the server + retrieves the handle from the cache and passes it to the + <code>sendfile()</code> (or <code>TransmitFile()</code> on Windows), + socket API.</p> + + + + <p>This file handle caching is done once at server start or + restart, only. So whenever one of the cached files changes on + the filesystem you <em>have</em> to restart the server (see the + <a href="../stopping.html">Stopping and Restarting</a> + documentation). To reiterate that point: if the files are + modified <em>in place</em> without restarting the server you + may end up serving requests that are completely bogus. You + should update files by unlinking the old copy and putting a new + copy in place. Most tools such as <code>rdist</code> and + <code>mv</code> do this.</p> + + + <div class="note"><h3>Note</h3> + <p>Don't bother asking for a directive which recursively + caches all the files in a directory. Try this instead... See the + <code class="directive"><a href="../mod/core.html#include">Include</a></code> directive, and consider + this command:</p> + + <div class="example"><p><code> + find /www/htdocs -type f -print \<br /> + | sed -e 's/.*/mmapfile &/' > /www/conf/mmap.conf + </code></p></div> + </div> +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="CacheFile" id="CacheFile">CacheFile</a> <a name="cachefile" id="cachefile">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Cache a list of file handles at startup time</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheFile <var>file-path</var> [<var>file-path</var>] ...</code></td></tr> +<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> +<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Experimental</td></tr> +<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_file_cache</td></tr> +</table> + <p>The <code class="directive">CacheFile</code> directive opens handles to + one or more files (given as whitespace separated arguments) and + places these handles into the cache at server startup + time. Handles to cached files are automatically closed on a server + shutdown. When the files have changed on the filesystem, the + server should be restarted to re-cache them.</p> + + <p>Be careful with the <var>file-path</var> arguments: They have + to literally match the filesystem path Apache's URL-to-filename + translation handlers create. We cannot compare inodes or other + stuff to match paths through symbolic links <em>etc.</em> + because that again would cost extra <code>stat()</code> system + calls which is not acceptable. This module may or may not work + with filenames rewritten by <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> or + <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p> + + <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">CacheFile /usr/local/apache/htdocs/index.html</pre> +</div> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="MMapFile" id="MMapFile">MMapFile</a> <a name="mmapfile" id="mmapfile">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Map a list of files into memory at startup time</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>MMapFile <var>file-path</var> [<var>file-path</var>] ...</code></td></tr> +<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> +<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Experimental</td></tr> +<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_file_cache</td></tr> +</table> + <p>The <code class="directive">MMapFile</code> directive maps one or more files + (given as whitespace separated arguments) into memory at server + startup time. They are automatically unmapped on a server + shutdown. When the files have changed on the filesystem at + least a <code>HUP</code> or <code>USR1</code> signal should be send to + the server to re-<code>mmap()</code> them.</p> + + <p>Be careful with the <var>file-path</var> arguments: They have + to literally match the filesystem path Apache's URL-to-filename + translation handlers create. We cannot compare inodes or other + stuff to match paths through symbolic links <em>etc.</em> + because that again would cost extra <code>stat()</code> system + calls which is not acceptable. This module may or may not work + with filenames rewritten by <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> or + <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p> + + <div class="example"><h3>Example</h3><pre class="prettyprint lang-config">MMapFile /usr/local/apache/htdocs/index.html</pre> +</div> + +</div> +</div> +<div class="bottomlang"> +<p><span>Available Languages: </span><a href="../en/mod/mod_file_cache.html" title="English"> en </a> | +<a href="../fr/mod/mod_file_cache.html" hreflang="fr" rel="alternate" title="Français"> fr </a> | +<a href="../ko/mod/mod_file_cache.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p> +</div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Libera.chat, or sent to our <a href="https://httpd.apache.org/lists.html">mailing lists</a>.</div> +<script type="text/javascript"><!--//--><![CDATA[//><!-- +var comments_shortname = 'httpd'; +var comments_identifier = 'http://httpd.apache.org/docs/2.4/mod/mod_file_cache.html'; +(function(w, d) { + if (w.location.hostname.toLowerCase() == "httpd.apache.org") { + d.write('<div id="comments_thread"><\/div>'); + var s = d.createElement('script'); + s.type = 'text/javascript'; + s.async = true; + s.src = 'https://comments.apache.org/show_comments.lua?site=' + comments_shortname + '&page=' + comments_identifier; + (d.getElementsByTagName('head')[0] || d.getElementsByTagName('body')[0]).appendChild(s); + } + else { + d.write('<div id="comments_thread">Comments are disabled for this page at the moment.<\/div>'); + } +})(window, document); +//--><!]]></script></div><div id="footer"> +<p class="apache">Copyright 2023 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p> +<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div><script type="text/javascript"><!--//--><![CDATA[//><!-- +if (typeof(prettyPrint) !== 'undefined') { + prettyPrint(); +} +//--><!]]></script> +</body></html>
\ No newline at end of file |